diepoxybutane 2,2'-bioxirane butadiene dioxide 2,2'-bioxirane bioxirane dioxybutadiene 1,3-butadiene diepoxide DEB Butadiendioxyd 1,1'-bi[ethylene oxide] 1,2:3,4-dianhydrothreitol butadiene diepoxide butane diepoxide 1,2:3,4-diepoxybutane 1,2:3,4-butadiene diepoxide mutagen epoxide